1. Technical Field
The present invention relates generally to electrosurgical coagulators and, more particularly, to an electrosurgical suction coagulator having improved thermal insulation between the active electrode and adjacent tissue.
2. Background of Related Art
The coagulation of bleeding blood vessels and tissue using electrically conductive suction tubes is a technique which has been widely used for some time. Typically, a combination electrosurgery and suction device is employed in surgery wherever excessive blood must be removed from the bleeding site in order to facilitate hemostasis of any bleeding vessels. More particularly, during any given surgical procedure, several layers of tissue usually must be penetrated to reach the operative field. When resecting an organ, for example, a gallbladder, the tissue surrounding the organ must be penetrated and dissected before the organ can be removed. The tissues being dissected, however, often contain blood vessels, nerves, lymph vessels, and the like, which should not be severed. The technique of blunt dissection is often used to prevent unnecessary damage caused by severing these vessels or nerves.
Blunt dissection, as opposed to sharp dissection, involves the use of a blunt surface to break through the tissue, thereby preventing the damage and bleeding caused by lasers and scalpels, the tools of sharp dissection. Hard surgical sponges, generally known as peanuts or Kittner sponges, or a surgeon's fingers are often used as blunt dissectors. A peanut is a tightly wound ball of absorbent material, such as gauze or other woven cotton, which is typically gripped with forceps and acts to abrade the tissue being dissected so that the dissection can be performed by either pulling on the tissue or by forcing the peanut through the tissue.
Laparoscopy, surgery performed through several small incisions made in the body rather than through a single large opening, has become the preferred method of performing certain procedures due to the reduced trauma and risk of infection as compared to normal, open surgical procedures. As a result, the use of conventional blunt dissectors, such as the peanut, during laparoscopic procedures presents many significant drawbacks. For instance, peanuts, being secured only by forceps, can become loose in the body. Further, the view of the operative field often becomes obstructed by pieces of tissue, blood and other bodily fluids produced during blunt dissection, necessitating the immediate need for both irrigation and aspiration of the operative field. Since it is undesirable to create additional incisions, the dissection must be stopped, the dissector must be removed, and an irrigator and/or aspirator must be inserted to remove the fluid and debris.
The use of electrical energy including radiofrequency and microwave energy and, in particular, radiofrequency (“RF”) electrodes or microwave antennae for ablation of tissue in the body or for the treatment of pain is known. For example, electrosurgery is a technique of using alternating current electrical signals in the approximately 200 kHz-3.3 mHz range that are generated by a source of electrosurgical energy, such as an electrosurgical generator, in connection with surgical instruments, to cut or coagulate biologic tissue endogenically. This electrosurgical signal can be a sinusoidal waveform operating in a continuous mode at a 100% duty cycle, or pulse modulated at a duty cycle of less than 100%. Typically, electrosurgical signals are operated at 100% duty cycle for maximal cutting effect, and are pulse modulated at duty cycles ranging from 50% to 25% for less aggressive cutting, or, at a substantially lower duty cycle of approximately 6%, for coagulating. The electrosurgical carrier signal may also be varied in intensity. The electrosurgical signal is applied to the patient via electrodes in either monopolar mode, or bipolar mode. In monopolar mode, the active electrode is the surgical instrument at the surgical site, and the return electrode is elsewhere on the patient, such that the electrosurgical signal passes through the patient's body from the surgical site to the return electrode. In bipolar mode, both the active and return electrodes are at the surgical site, such as with an instrument having an array of electrodes, so that the electrosurgical signal passes only through the tissue situated between the RF electrodes of the instrument.
Electrosurgical suction coagulators which both coagulate and dissect tissue have also been available for some time. Generally, these devices include a shaft formed from a conductive suction tube electrode having an electrically insulating coating over all but a most distal portion of the tube, so that the distal portion forms a generally annular ablating electrode. The shaft may be formed of malleable materials to enable a surgeon to bend the shaft to a desired shape. The distal end can be used as a blunt dissection device and/or a blunt coagulator. A suction source is attached to a proximal portion of the tube for evacuating excess fluid and debris from the surgical site through the distal end of the tube. The electrode is operably coupled to a source of electrosurgical energy, such as an electrosurgical generator.
The described electrosurgical suction coagulators may have drawbacks. In particular, heat conducted from the suction tube electrode to the outer surface of the shaft may cause the surface of the shaft to reach temperatures of 60° C. or greater. This may be a concern during surgical procedures, such as an electrosurgical adenotonsillectomy, where the shaft of a suction coagulator may be in proximity to, or in contact with, anatomical structures unrelated to the procedure, such as the uvula or the oral commissure. The elevated shaft temperature may have undesirable effects on such unrelated anatomical structures, including uvular edema and erythema of the oral commissure area. An electrosurgical suction coagulator which avoids or minimizes such undesirable effects would be a welcome advance in the art, particularly when such benefits are realized in a rugged, reliable, and relatively simple design.